Field of the Invention
The invention relates to a two-chip power IC, in which a sensor chip having a sensor is mounted on a switch chip having a switch. The sensor is electrically connected to the switch in order to switch it off when the temperature detected by the sensor exceeds a preset threshold value.
Examples of such two-chip power ICs includes a Tempfet ("temperature protected FET") and a Profet ("protected FET"). These two-chip power ICs are effectively resistant to short-circuits, in the event of the short-circuit current being reduced as well, only if the temperature detection ("temperature sensing") can be carried out reliably by means of the sensor chip which is bonded to the switch chip. This means that the temperature sensor (also referred to, for short, as the "sensor" in the following text) must reliably be able to detect a temperature rise in order to be able to switch the switch in the switch chip off in good time before it is destroyed by a short-circuit current. However, this presents a problem when the short-circuit current values are reduced and do not result in the sensor on the sensor chip being heated sufficiently.
In general, the maximum permissible gate-source voltage of a switch, which is generally an FET, in the switch chip must not exceed a specific maximum value in order that the switching-off process in the event of a short-circuit can still be carried out in good time before the switch is destroyed. Even in the case of a sensor chip which is bonded on to the switch chip, it has been found that it is impossible to ensure that the switch chip is reliably switched off in good time, since in many cases the sensor chip is heated only relatively slowly. This is due to the fact that the encapsulation compound which encloses the switch chip and the sensor chip causes the sensor chip to be additionally cooled. As a result, the heating of the switch chip produced before a short-circuit occurs is not sufficient to heat the sensor chip so that the sensor can switch off the switch in the switch chip.
European patent application EP 0 262 530 A1 describes a configuration comprising a power semiconductor chip and a control circuit which is integrated in a second semiconductor chip. The semiconductor chip, together with the control circuit, is thereby mounted on one of the surfaces of the power semiconductor chip, with the two semiconductor chips being connected to one another by means of an insulating layer and a solder layer. The semiconductor chip together with the control circuit is electrically connected via electrical lines to the power semiconductor chip.
The configuration is mounted on a lead frame. The source contact of the power semiconductor chip is connected via two bonding wires to in each case one connecting finger of the lead frame and to one contact of the sensor chip.